Response to village idiot's w/u, below:
Oh, I don't spoil my children - not more than any other parent...at least, I don't happen to think so.
I am merely musing on the nature of this behaviour, which I have seen so frequently. I think the underlying reason is that children ask you for material things (whether or not they are given them) as a signal to you that they need you. It may be a clumsy, heavy-handed sort of signal - but nobody ever said that children were sophisticated or subtle. And, again: Isn't it great to feel needed?

Not to rain on your parade, but if you give your kids stuff just because they ask for it, they'll start to expect it, and it won't take long before they're demands start being pretty expensive. And when the time comes that the price tags on the toys they want are more than you're willing to pay, they won't understand, and will be very upset. Sure, an ice cream cone here and an action figure there might seem a small price to pay for so much perceived happiness from your little bundle of joy, but both you and your kid's sanity are at much less risk ten years from now (at least from the effects of spoiled brat syndrome) if you don't start the dangerous pattern of letting him or her think that their greediness is justified so early on.

As a general rule, just remember how (completely)impressionable children are -- their belief systems and world outlook are being created based on the experiences you expose them to.
See developmental stage, imprinting